it may be Dolman, they are going by, or cutting through shipstones. Skeles will actually respawn at the dolman every now and then. Loose items can be found near either. Randomly. If you map mark them, you can always collect stuff later. Do them on slow times, waiting for kilns smelting etc. Take an antler enough wood to throw a table and have at it. Or make a copy of you map and cut the ground up in there. I am not a big fan of scarring my world up in a permanent way. I'd rather do it on a throw-away copy. I just messed up the ground some at my fort, my main save, and largest build/establishment. Rebuilding the land is tedious and erratic at best, Voxels getting abnormally stretched. It leaves awkward pits in the ground that don't want to be easily fixed. It's a pain.